The project describes the design of controlled inverters or power generator simulating one phase of European or American distribution network. The generator is able to enter into an output signal of a certain fault conditions designed to testing the electromagnetic compatibility of connected devices. The text is divided into three main chapters. The first one deals with the design of the power generating low-frequency signal. The second part describes the power source used for this generator. In the third section describes the program management unit. End of text summarizes the results. The annex contains a schematic designs and printed circuit boards.

This work proposes recommendations for new guidelines for fault current injection on a distribution grid. These guidelines will help improve the transition towards renewable electrical energy generation. The grid-integration of inverter-based distributed generations (IBDGs) into the distribution grid changes the topology of a conventional grid with one-way power flow to a grid with multi-way power flow. This thesis investigates the impact of fault current injection on a distribution grid, if the limitations in the fault current injection of IBDGs affect the reliable function of the protection system and if there is a preferable type of current control to be prioritised. This investigation was carried out through a literature review and transient state simulations on a model grid in PSCAD. The grid is based on a real radial distribution grid on the Swedish island of Gotland, where a Type III wind turbine generator (WTG) is connected. The limitation on fault current injection by the wind turbine, the location and type of fault in the grid, can affect the reliable function of the protection system. The control system inside a type III WTG affects its fault current injection that impacts fault detection by the protection system. This thesis emphasizes the need for a guideline and requirement on the WTG control system for fault current injection. Prioritising reactive current control (q-axis) seems to be preferable and should become the standard for fault current injection in type III wind turbine generators in this distribution grid, according to this study. Furthermore, the need for more investigation for different types of IBDGs with different control strategies is highlighted in this work. / Detta arbete föreslår rekommendationer för nya riktlinjer för felströmsinjektering i ett distributionsnät. Dessa rekommendationer kommer bidra till att förbättra omställningen till förnyelsebar elgenerering. Integreringen av omriktarbaserade distributionsgeneratorer (IBDG) i distributionsnätet förändrar topologin i ett konventionellt nät med ett enkelriktat effektflöde till ett flervägsriktat effektflöde. Detta examensarbete undersöker påverkan av felströmsinjektering i ett distributionsnät, om begränsningarna i felströmsinjekteringen hos IBDG:er påverkar reläskydds pålitliga funktionalitet och om det finns en typ av kontrollström som föredras och bör prioriteras. Denna undersökning genomfördes genom en litteraturstudie och transienta simuleringar i ett exempelnät i PSCAD. Nätet är baserat på ett verkligt radialdistributionsnät från Gotland, där ett Typ III vindkraftverk (WTG) är anslutet. Begränsningen i felströmsinjektering hos vindkraftverket, platsen för och typen av fel i nätet kan påverka den pålitliga funktionaliteten hos reläskydd. Kontrollsystemet inuti ett Typ III WTG påverkar dess felströmsinjektering som påverkar feldetekteringen i reläskyddet. Detta examensarbete betonar vikten av riktlinjer och krav på WTG kontollsystem för felströmsinjektering. Prioritering av reaktiv kontrollström (q-axis) verkar vara fördelaktigt och bör bli standard för felströminjektering i Typ III WTG i detta distributionsnät, enligt detta arbete. Dessutom påtalas behovet av att ytterligare undersöka olika typer av IBDG:er med olika kontrollstrategier i detta arbete.

The world is heading towards an energy crisis and desperate efforts are being made to find an alternative, reliable and clean source of energy. Solar Energy is one of the most clean and reliable source of renewable energy on earth. Conventionally, extraction of solar power for electricity generation was limited to PV farms, however lately Distributed Generation form of Solar Power has emerged in the form of residential and commercial Grid Tied Micro-Inverters. Grid Tied Micro-Inverters are costly when compared to their string type counterparts because one inverter module is required for every single or every two PV panels whereas a string type micro-inverter utilizes a single inverter module over a string of PV panels. Since in micro-inverter every panel has a dedicated inverter module, more power per panel can be extracted by performing optimal maximum power tracking over single panel rather than over an entire string of panels. Power per panel extracted by string inverters may be lower than its maximum value as few of the panels in the string may or may not be shaded and thereby forming the weaker links of the system. In order to justify the higher costs of Micro-Inverters, it is of utmost importance to convert the available power with maximum possible efficiency. Typically, a microinverter consists of two important blocks; a Front End DC-DC Converter and Output DCAC Inverter. This thesis proposes efficiency optimization techniques for both the blocks of the micro-inverter. iv Efficiency Optimization of Front End DC-DC Converter This thesis aims to optimize the efficiency of the front end stage by proposing optimal design procedure for resonant parameters of LLC Topology as a Front End DC-DC Converter for PV Applications. It exploits the I-V characteristics of a solar panel to design the resonant parameters such that resonant LLC topology operates near its resonant frequency operating point which is the highest efficiency operating point of LLC Converter. Efficiency Optimization of Output DC-AC Inverter Due to continuously variable irradiance levels of solar energy, available power for extraction is constantly varying which causes the PV Inverter operates at its peak load capacity for less than 15% of the day time. Every typical power converter suffers through poor light load efficiency performance because of the load independent losses present in a power converter. In order to improve the light load efficiency performance of Three Phase Inverters, this thesis proposes Phase Skipping Control technique for Three Phase Grid Tied Micro-Inverters. The proposed technique is a generic control technique and can be applied to any inverter topology, however, in order to establish the proof of concept this control technique has been implemented on Three Phase Half Bridge PWM Inverter and its analysis is provided. Improving light load efficiency helps to improve the CEC efficiency of the inverter.

With the ongoing surge in electrification within the automotive industry, the demand for high-power inverters is steadily on the rise. Furthermore, these inverters are now expected to handle increased power loads while maintaining enhanced efficiency. Fulfilling these demanding prerequisites, places significant importance on the current sensors that meticulously monitor each phase of the inverter. This thesis tackles the deep study of a current sensor that has been chosen by Scania to be introduced in the new generation of inverters. The chosen sensor is based on the Integrated Magnetic Concentrator (IMC)- Hall technology. Given its innovative nature within the company’s scope, there exists a keen interest in investigating its performance. The principal parameters that will be assessed during this thesis are accuracy, temperature dependencies, bandwidth and noise immunity. The evaluation of these properties will be done though the creation of a test rig capable of producing current pulses, spanning the range necessary for the sensor evaluation. A high-end current sensor based on the fluxgate technology will be used as a reference during the assessment. Across the course of the research, diverse experiments and modifications to the testing setup will be undertaken to accommodate the assessment of each individual parameter. The acquired data will be summarized and presented with simplified figures. The results of this study show that the accuracy of the sensor highly depends on a proper end of line calibration and a mechanical assembly, in other words, the sensor must be perfectly centered within the IMC. Moreover, the study identifies linear relationships between temperature and accuracy, while exponential correlations are found between the impact of an external magnetic field and its distance. / Med den pågående ökningen av elektrifiering inom fordonsindustrin ökar efterfrågan på högeffektsväxelriktare stadigt. Dessutom förväntas dessa växelriktare nu hantera ökad effektbelastning samtidigt som de bibehåller förbättrad effektivitet. Att uppfylla dessa krävande förutsättningar lägger stor vikt vid strömsensorerna som noggrant övervakar varje fas i omriktaren. Denna avhandling tar upp den djupgående studien av en strömsensor som har valts ut av Scania för att introduceras i den nya generationen växelriktare. Den valda sensorn är baserad på Integrated Magnetic Concentrator (IMC)- Hall-teknologi. Med tanke på dess innovativa karaktär inom företagets ram finns det ett stort intresse för att undersöka dess prestationer. De huvudsakliga parametrarna som kommer att bedömas under detta examensarbete är noggrannhet, temperaturberoende, bandbredd och brusimmunitet. Utvärderingen av dessa egenskaper kommer att göras genom skapandet av en testrigg som kan producera strömpulser som spänner över det intervall som krävs för sensorutvärderingen. En avancerad strömsensor baserad på fluxgate-tekniken kommer att användas som referens under bedömningen. Under forskningens gång kommer olika experiment och modifieringar av testuppsättningen att genomföras för att tillgodose bedömningen av varje enskild parameter. De insamlade uppgifterna kommer att sammanfattas och presenteras med förenklade siffror. Resultaten av denna studie visar att sensorns noggrannhet i hög grad beror på korrekt ”end of line” kalibrering samt mekanisk montering. Med andra ord måste sensorn vara perfekt centrerad inom IMC. Dessutom identifierar studien linjära samband mellan temperatur och noggrannhet, medan exponentiella korrelationer finns mellan påverkan av ett externt magnetfält och dess avstånd.

Master of Science / Department of Electrical Engineering / William B. Kuhn / During the development of an educational renewable energy production platform, it was found that there were no low-cost, efficient grid-tie interfaces for a 160 W DC wind turbine. Typically, a small DC wind turbine is used in conjunction with a rechargeable battery bank or, if the wind turbine is directly interfaced with a grid-tie inverter, a regulator with a diversion-load. The use of batteries is undesirable due to their high-cost and high-maintenance characteristics. Diversion loads by nature waste power, as any excess energy that cannot be accepted by a battery or inverter is usually converted into heat through a resistive element. Initially, a 24 V DC, 160 W Air Breeze small wind turbine was directly connected to an Enphase Energy M190 grid-tie micro-inverter. The 24 V DC Air Breeze wind turbine is designed to charge a battery or bank of batteries while the M190 micro-inverter is designed to convert the DC output of a 200 W solar panel to grid-tied AC power. As expected, the power-production response time associated with the small wind turbine and the power-accepting, load-matching response time of the micro-inverter were not compatible. The rapidly changing power output of the small wind turbine conflicted with the slow response time of the micro-inverter resulting in little power production. Ultimately, the response time mismatch also produced sufficiently large voltage spikes to damage the turbine electronics. In this thesis, a solution for a low-cost, efficient grid-tie interface using no batteries and no diversion load is presented. A capacitance of eight Farads is placed in parallel with the small wind turbine and the micro inverter. The large capacitance sufficiently smoothes the potential abrupt voltage changes produced by the wind turbine, allowing the micro-inverter adequate time to adjust its load for optimal power conversion. Laboratory experiments and data from an implementation of such a parallel super capacitor wind turbine to grid-tie micro-inverter configuration are provided along with DC and AC power production monitoring circuits interfaced with a micro controller.

This thesis focuses on the single-phase voltage-source inverter for use in photovoltaic (PV) electricity generating systems in both stand-alone and grid-tied applications. In many cases, developments in single-phase PV systems have followed developments in three-phase systems. Time-variant systems are more difficult to control than time-invariant systems. Nevertheless, by using suitable transformation techniques, time-variant systems can often be modelled as time-invariant systems. After the transformation, the control signals that are usually time-variant (often varying sinusoidally in time) become time-invariant at the fundamental frequency, and are hence much easier to deal with. With this approach, synchronous rotating frame control techniques have been previously proposed for high performance three-phase inverter applications. The transformation theory cannot be applied directly in single-phase systems without modification, and the d-q components would not be time-invariant in situations where harmonics, resonances or unbalance is present. Single-phase inverter controller designs based on the use of a synchronous rotating reference frame have been proposed, but such designs do not always perform as well as expected. This thesis aims to improve single-phase voltage-source inverters. The main objective is to address, in terms of cost, efficiency, power management and power quality, the problems found with single-phase designs based on a synchronous rotating frame single-phase inverter controller. Consequently, this thesis focuses on a novel controller approach in order to obtain a more reliable and flexible single-phase inverter. As the first step, this thesis investigates the single-phase inverter switching gate-drive algorithms and develops a form of space-vector pulse-width-modulation (SVPWM) in order to reduce total harmonic distortion. The results of the new SVPWM algorithm demonstrate its superior performance when compared with sinusoidal pulse-width-modulation (SPWM) which is often used with single-phase inverters. The second step, which is further reviewed and presented in this thesis, is the modelling of the single-phase inverter control based on the synchronous rotating frame. A mathematical analysis is conducted to determine the mechanism of the coupling that exists between the voltage phase and amplitude terms, and a new transformation strategy is proposed based on using the voltage phase as a reference at the Park transformation stages, and the current phase as a reference for the current at the transformation stages. The line-frequency components of the feedback signals are transformed to time-invariant components, thus eliminating the ripple and reducing the computational burden associated with the controller stage. Consequently, the inverter feedback controller stage is designed so that the coupling terms are decoupled within the controller itself. The effectiveness of the techniques proposed in this thesis are demonstrated by simulation using the MATLAB/SIMULINK environment. The proposed technique was also investigated through a practical implementation of the control system using a Digital Signal Processor (DSP) and a single-phase inverter. This practical system was tested up to 1 kW only (limited by the available inverter hardware). Nevertheless, the correlation between the simulation and the practical results is high and this gives confidence that the developed mechanism will allow the 2.5kW goal to be achieved. Practical test cases illustrate the effectiveness of the models. In addition, the comparisons between experimental and simulation results permit the system's behaviour and performance to be accurately evaluated. With the development of the new controller, small-scale single-phase renewable energy systems will become more useful in the field of power quality management through their ability to separately control the phase and amplitude of the output voltage. Consequently, incorporation of this type of generator within the national electrical distribution network, as distributed generators (DG) at low-voltage level, can assist with power quality management at the consumer side of the grid. In addition, such a generator can also operate in stand-alone mode if the grid becomes unavailable. The third step in this thesis investigates small-scale single-phase renewable energy systems operating as decentralized distributed generators within a local network. This operation is achieved by controlling the inverter side using the quantities measured at the common coupling point between the grid and the inverter, without requiring other extensive communications. Thus, the small-scale single-phase renewable energy distributed generator systems will contain only a local controller at each installation.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2008. / The design of an aperture-coupled coaxial diplexer for R-band, is presented. To improve the ease of tuning, a tuning procedure for the diplexer with the aid of a MATLAB application with graphical user interface, is developed. Final experimental results show good agreement between the circuit model and the physical structure. Final measurements of the diplexer structure achieved 18.83 dB and 21.52 dB return loss in the lower and upper frequency band respectively and insertion loss of 0.58 dB and 0.61 dB was measured for the two frequency bands. Isolation were measured as 74 dB at 2.01 GHz and 84 dB at 2.17 GHz The accuracy of two techniques for determining coupling coefficients in coaxial and waveguide resonators are investigated. One method is the Eigenmode Method for determining the coupling coefficients in a physical resonator and the other the circuit model representation, utilising inverters to represent the coupling between resonators. Results showed that marked differences occur when using the three different inverter configurations to enable filter dimensioning for a given coupling coefficient. Four waveguide filters, utilising posts and irises respectively, are designed using dimensions obtained from the three inverter configurations as well as the Eigenmode method for a certain coupling coefficient.

<p>En av Glimek AB:s mest förekommande maskiner är SD-180 som används för degavvägning. Den finns i flera olika varianter. Den enklaste har enbart start- och stoppknapp och en potentiometer för att ställa hastigheten och en mer avancerad variant har en operatörspanel där olika möjligheter till inställningar finns.</p><p>Konstruktionen på denna maskin hade inte uppdaterats på många år och behövde en uppdatering av användargränssnitt, programvara och elkonstruktion. Arbetet har framförallt koncentrerat sig på användargränssnittet till panelen.</p><p>En del av arbetet var att undersöka om det var möjligt att utesluta PLC ur konstruktionen och använda en mer avancerad programmerbar frekvensomformare. Eftersom det blev problem med lanseringen av programvara till frekvensomformaren och enbart en mindre bra fungerande demoversion fanns tillgänglig så var detta tyvärr inte möjligt.</p><p>I arbetet har olika varianter på operatörspaneler utretts. Exempel på flödesdiagram till PLC har också gjorts.</p> / <p>One of Glimek AB's most common machines is the dough divider, SD-180. It is available in many different variants. The simplest has only a start- and stop button and a potentiometer to set the speed. A more advanced version has an operator panel with various options.</p><p>The design of this machine had not been updated in many years and needed an update of the user interface, software and electrical construction. The thesis has mainly concentrated on the human machine interface.</p><p>A part of the work was to investigate whether it was possible to exclude the PLC from the design and use a more powerful and programmable frequency inverter.Unfortunately problems arose with the release of the software for the frequency converter. Only a demo version of the software where available and it was not possible to this study because of that.</p><p>Different variants of human machine interface have been investigated. An example flowchart diagram to the PLC has also been made.</p>

This thesis presents a new output passive filter for voltage source inverter applications which is based on a shunt connected single tuned filter topology. The proposed circuit has the advantage of tracing harmonic components wherever its location in the frequency spectrum. The change in the harmonic location might be as a result of a change in the inverter operating frequency. Also, the proposed filter achieves harmonic reduction close to the traditional single tuned passive filter. In order to show the superiority of the proposed model, a comparison is introduced with other self tuning harmonic filters showing merits and drawbacks of each technique. The proposed circuit (when integrated in square wave inverter) has also shown a tremendous reduction in the switching losses in comparison with high frequency Pulse Width Modulation inverter. Mathematical analyses showing the design of the proposed filter together with extensive simulation results to verify the design are also introduced. The practical implementation of the system is presented and the results show excellent agreement with the theory and simulation. In order to appreciate the proposed filter a new method for classifying passive power filters is introduced. The review includes a comparison of these configurations showing their merit and drawbacks.

Este trabalho tem como principal objetivo apresentar um estudo, uma modelagem e uma simulação de um inversor de comutação suave para aplicação em um filtro ativo para instalações de baixa e média potência. Inicialmente apresenta uma revisão bibliográfica sobre inversores de comutação suave, onde os mesmos são classificados em função do local onde o circuito auxiliar de comutação suave está inserido, gerando três classificações básicas: comutação de linha, comutação de carga e comutação de chave. Três processos de comutação suave são apresentados: comutação em zero de tensão, comutação em zero de corrente e comutação em zero de corrente e zero de tensão. Dentro deste contexto apresentam-se as diversas topologias de inversores de comutação suave. Uma análise de comutação de um inversor em um filtro ativo monofásico é apresentada e o inversor ZCT com duas chaves auxiliares é selecionado para ser aplicado no referido filtro. Uma modelagem completa do inversor ZCT com duas chaves auxiliares é apresentada e corroborada pela comparação dos resultados de simulação obtidos a partir do modelo teórico com os resultados obtidos por meio de simulações realizadas no SPICE. A Modelagem do inversor ZCT com duas chaves auxiliares culmina em uma nova metodologia de projeto, onde é possível determinar com grande exatidão a máxima corrente de carga para a qual o inversor ainda opera no modo ZCT. Diversas simulações realizadas no Simulink/Matlab e no SPICE comprovam as comutações suaves em zero de corrente nas chaves do inversor e também o desempenho dinâmico do mesmo quando operando em um filtro ativo paralelo. / This work shows the study, the selection and the analysis of a soft-switched inverter for an ac single-phase active power filter. For this, various topologies of the soft-switched inverters are classified based upon the location of the auxiliary circuit and the topology that achieves the goals for application in the active power filter is selected. Three commutation processes are presented: zero voltage switching (ZVS), zero current switching (ZCS) and zero current and zero voltage switching (ZCZVS). The ZCT inverter with 2 auxiliaries switches is selected for the application in an ac single-phase active power filter: this topology reduces the turn-on losses and practically eliminates the turn-off losses of all IGBTs of the inverter. Some new guidelines to project the ZCT inverter with 2 auxiliaries switches are presented, achieving an accurate calculation of the maximum load current for operation in ZCT. The results of the simulation from Simulink/Matlab and SPICE prove some goals of the ZCT inverter: the ZCT inverter with 2 auxiliaries switches reduces the total losses when compared with the hard-commutation inverter and the dynamic performance of the ZCT inverter applied in an ac single-phase active power filter is showed.